Prevalence of Tuberculosis in Sub-Saharan Afri
By Brooke Heaton
Published Winter 2022
Special thanks to Jamie LeSueur for editing and research contributions
Summary+
Tuberculosis is an endemic problem for much of the sub-Saharan African region. High infection rates, caused by high population density and the infrastructure of the living environment, contribute to high infection rates, as well as compromised immune systems from diseases such as HIV/AIDS and health issues like malnutrition . The insufficient infrastructure of medical care and the underutilization of such also contribute to the perpetuation of the disease. Tuberculosis negatively affects the physical health of infected individuals, whose effects can be long-lasting and decrease quality of life. It can also lead to the social rejection of those infected and place enormous economic burdens on patients and families. The adopting of emerging data regarding new treatment regimens for the disease has the potential to decrease the likelihood of transmissibility in areas, leading to decreased cases and a tapering effect on the disease.
Key Takeaways+
Key Terms+
High Population Density—Measurement of population per unit area.
HIV/AIDS—HIV (human immunodeficiency virus) is a virus that attacks the body's immune system. If HIV is not treated, it can lead to AIDS (acquired immunodeficiency syndrome).
Malnutrition—Lack of proper nutrition, caused by not having enough to eat, not eating enough of the right things, or being unable to use the food that one does eat.1
Morbidity—The condition of suffering from a disease or medical condition.2
Sputum—Mixture of saliva and mucus coughed up from the respiratory tract, often a sign of infection.
Sub-Saharan Africa—From or forming part of the African regions south of the Sahara desert, including 48 of the 54 African countries.3
Tuberculosis—An infectious bacterial disease characterized by the growth of nodules (tubercles) in the tissues, especially the lungs.4
Context
Q: What is tuberculosis?
Tuberculosis is a treatable, curable disease, but remains the ninth leading cause of death worldwide, claiming 1.4 million lives in 2019.5 Tuberculosis is a disease caused by the agent Mycobacterium tuberculosis and is spread from person to person through droplets in the air.6 These droplets exit an infected person by coughing or sneezing and they can enter another person if they inhale air containing these droplets, causing the person to become infected. Contagion requires that the individuals be in close proximity to one another.7 There are two stages of tuberculosis: latent tuberculosis infection and active tuberculosis disease.8 Upon initial infection, all patients will contract latent tuberculosis which may then progress to active tuberculosis depending on the health of the individual. It is estimated that the global prevalence of latent tuberculosis comprises nearly 25% of all tuberculosis cases.9 Individuals with latent tuberculosis infection do not have signs and symptoms and cannot spread the infection to others. When an individual with latent tuberculosis has a weakened immune system, the infection will become active and turn into tuberculosis disease. Those with active tuberculosis disease can spread the infection, and they often experience symptoms such as chronic coughing, weight loss, fever, fatigue, chest pain, and they often cough up blood. Many patients that have active tuberculosis do not show symptoms right away, especially women, children, and pregnant women. In fact, 50–60% of those with tuberculosis do not experience chronic coughing and 15–25% do not experience any symptoms.10
Q: Is tuberculosis treatable?
Tuberculosis is treatable and the treatment is highly effective, the success rate being 80% for drug-sensitive tuberculosis11 The treatment includes a six to nine month course of two different antibiotics, isoniazid and rifampicin, or a combination of both taken seven days a week for 26 weeks.12, 13, 14 If a patient stops taking the antibiotics before completing the course or skips a dose, this may lead to resistance to the two antibiotic treatments, causing drug-resistant tuberculosis.15 Other drugs have been developed to treat this type of tuberculosis but the success rate of those treatments is only 48% worldwide.16 While tuberculosis is treatable, it is not preventable, despite the availability of the Bacillus Calmette-Guerin (BCG) vaccine. This vaccine can reduce the effects of tuberculosis in children. However, little evidence has been found to show that the BCG vaccination decreases TB related mortality rates for adults.17
Q: Who is most susceptible to tuberculosis?
Because latent and active tuberculosis are prevalent in different groups and affect people differently, those susceptible to each varies. Risk factors for becoming infected with latent tuberculosis are mostly external factors, such as living in a group or area with high infection rates or being in close contact with someone who has active, or infectious, tuberculosis.18 Tuberculosis can infect anyone but most often becomes active in those who are living with immunocompromising conditions that weaken an immune system's ability to fight off infections such as HIV/AIDS, increasing the chances of mortality.19 Malnutrition also contributes to the likelihood of tuberculosis progressing to the active disease which most often affects children, contributing to tuberculosis being the leading cause of global child mortality.20
Q: Where in the world is tuberculosis a big issue?
Tuberculosis is principally a disease of poverty, with 95–98% of deaths occurring in developing countries and over 25% of those occurring in Africa In 2016 alone, 2.5 million people fell ill with tuberculosis in sub-Saharan Africa, accounting for a quarter of new tuberculosis cases worldwide. Other areas of the world are also affected by tuberculosis, such as the South-East Asian region which accounts for 43% of new cases and the Western Pacific region accounts for 18%. In 2020, 86% of new cases occurred in 30 high-burden countries, 16 of which are in the African region.21, 22, 23 Looking at specific countries within the sub-Saharan African region, one study found that 31.2% of the Ethiopian population has latent tuberculosis, 49% of the Ugandan population, and 55.2% of the South African population. In 2019 in the Democratic Republic of the Congo, tuberculosis was the third leading cause of mortality.24, 25, 26
Q: What countries does sub-Saharan Africa include?
The continent of Africa is made up of 54 countries. The sub-Saharan African region includes 48 of those countries, excluding only Algeria, Egypt, Libya, Morocco, Sudan, and Tunisia.27 One limitation of this paper is the massive geographical area and the general claims made for such a large number of diverse countries, cultures, tribes, and languages. A lack of data and research about tuberculosis conducted in each of these areas makes only a study including the whole of sub-Saharan Africa possible. Recognizing that an accurate depiction of the prevalence of tuberculosis in each of these areas cannot currently be portrayed, throughout this paper, studies from different countries and areas will be used to illustrate common themes and consequences regarding the shared contributing factors and negative consequences of tuberculosis.
Q: How long has tuberculosis been an issue in sub-Saharan Africa?
Though tuberculosis has been around for thousands of years, it was officially discovered and named by scientists in 1882.28 In 2004, the incidence of tuberculosis in the sub-Saharan African region was 359 per 100,000. In 2014 this number dropped to 283 per 100,000 and in 2019 it was 226.29 Despite these improvements, case detection rates in sub-Saharan Africa are still estimated to be only 57%, meaning that nearly half of all cases in this area are not diagnosed.30
Contributing Factors
High Infection Rates
High Population Density
High population density directly contributes to the high infection rates in sub-Saharan Africa due to close contact and shared air spaces, increasing the chances of infection. High population density coincided with higher tuberculosis incidence rates in two different districts in Botswana. The incidence rate varied considerably by geography, ranging from 66 tuberculosis patients per 100,000 persons in the less densely populated suburban areas of the Gaborone district to 1,140 tuberculosis patients per 100,000 persons in the densely populated remote, rural villages of the Ghanzi District.31 The more individuals that reside in an area, the more likely they are to be in close quarters with one another and be exposed to diseases that others in the area may carry.
Mauritius is the most densely populated country in sub-Saharan Africa with 626.5 people per square kilometer with Rwanda having 525 people per square kilometer, Burundi at 463 people per square kilometer, and Malawi at 203 people per square kilometer.32 To put this in perspective, the population density of the state of Utah in 2020 was about 15.33 people per square kilometer.33 There are 48 countries in sub-Saharan Africa, 41 of which have a population density greater than the state of Utah. Many factors have reduced the amount of habitable land in sub-Saharan Africa such as climate, vegetation, and agriculture, creating many densely populated areas within each country.34
Communal Living
One contributing factor of the high rate of transmission in places like sub-Saharan Africa is the cultural lifestyle, which is very socially interconnected.35 While not exclusive to sub-Saharan Africa, people in this region often live in dense groups that share much in common such as living spaces, markets, and social venues, contributing to high infection rates of tuberculosis. Many individuals live in compounds or connected housing that shares an outdoor kitchen, bathroom, and yard. Members from these households spend ample time outside with one another, which can lead to tuberculosis infection because they are in close proximity to one another.36 Median daily contacts from non-household socialization for adult South Africans was 40 individuals daily with 25.5 being strangers contacted through public transportation.37 In a separate South African study, non-repeated contacts contributed to 51% of contact time, and researchers associate non-repeated contacts with 79% of tuberculosis transmission.38 These elements of communal life can increase the possible proximate risk factors, or direct exposure to infectious droplets.
Compromised Immune Systems
HIV/AIDS
The severity of the tuberculosis crisis in sub-Saharan Africa is exacerbated by the prevalence of HIV/AIDS in the region. HIV/AIDS are immunosuppressive conditions that weaken the immune system, increasing the likelihood of developing active tuberculosis disease. When treated, the presence of latent tuberculosis in an individual is not life-threatening. However, those who have HIV and then become infected are 20–30 times more likely to develop active tuberculosis, which is life threatening.39 These patients are ill equipped to fight off the infection because of their preexisting immunocompromised state which compounds their symptoms and often leads to death.40 Globally, tuberculosis was the leading killer of HIV-positive people in 2016, accounting for 40% of deaths.41
In 2015, 1.2 million new tuberculosis cases were diagnosed amongst individuals who were HIV-positive, and 71% of these individuals were living in the African region.42 In Zambia, the presence of tuberculosis was five times higher among HIV-positive individuals than HIV-negative.43 Of 16,000 tuberculosis cases in Blantyre, Malawi from 2011–2018, 70.3% were HIV-positive and 29.7% were HIV-negative.44 A recent study of nine African countries found that the presence of HIV in a patient also reduces the effectiveness of tuberculosis treatment, citing that 80% of non-HIV patients were relapse free after the treatment as opposed to 72.5% of patients with both HIV and tuberculosis.45
Undernutrition
Research conducted in South Africa shows that undernutrition places people at a higher risk for contracting tuberculosis and a lower chance of surviving since malnourished individuals have weakened immune systems.46 In a recent study, 84.3% of children with tuberculosis disease were also diagnosed as malnourished, a double diagnosis which is associated with longer recovery times for children in sub-Saharan Africa.47 In Ethiopia, tuberculosis has been found to be present in 21.5% of severe malnutrition cases, showing that it is the most common chronic infection associated with severe malnutrition.48 Apart from malnutrition making individuals more likely to contract tuberculosis, it also acts as a barrier to effective tuberculosis treatment for those infected. Malnourishment is a wasting disease, causing patients to lose weight, often affecting treatment outcome because dosage must be reduced as body weight decreases, to avoid side effects, which, if not adjusted, often cause patients to discontinue treatment.49 Additionally, treatment medication is most effective when taken with food, which can be an obstacle for individuals living in poverty that do not have regular access to food.50 This is clearly an issue in sub-Saharan Africa, as shown by a 10 year meta-analysis of 32 studies conducted in sub-Saharan Africa where the pooled prevalence of malnutrition was 33.2%.51 Among a group of South Africans that had tuberculosis, 34% were underweight.52
Insufficient and Unutilized Medical Care
Medical Care Infrastructure
A lack of proper medical care infrastructure perpetuates the disease, leading to many individuals being infected, spreading it to others unknowingly, and failing to complete treatment.53 Distance to treatment centers, capacity of testing laboratories, delay in health services, and poor quality of care are all aspects of the infrastructure of medical care.54 Many of these services are lacking in areas of sub-Saharan Africa.
Only 60% of individuals included in the 2018 estimated total tuberculosis burden in Zambia had access to testing and only 50% had access to treatment.55 Individuals who lack access to testing services may live in areas without any primary health facilities or tuberculosis facilities nearby, or they may be temporarily outside of areas with facilities while performing seasonal labor such as farming.56 In Malawi, a distance of greater than 10 kilometers to a treatment center was associated with a greater number of days between the onset of symptoms and the first time the patient received medical care.57 In Ethiopia, patients living in rural areas had a three times increase in patient delay times compared to those living in urban areas.58 15% of Kenyan patients cited difficulty reaching health facilities as the reason they discontinued their treatment.59
Those who lack access to treatment may have been misdiagnosed or may be experiencing a delay between testing and treatment.60 In Chad, the median healthcare system delay, or the time between the first formal health care received and the initiation of treatment, was 36 days.61 In Uganda, the delay was 56 days and in Malawi it was 59 days.62, 63 This increases the chance of those experiencing active symptoms infecting a greater number of people, perpetuating the disease. The level of service also impacts treatment, such as in Uganda, where over 90% of patients visited more than one healthcare provider and had an average of four visits before receiving a diagnosis of tuberculosis.64 In Malawi, four weeks after the onset of symptoms, only 9.1% of patients were started on a treatment medication.65 Ultimately, because of a lack of infrastructure in medical care, massive uncertainty exists about the incidence, mortality, and effects of tuberculosis in sub-Saharan Africa.66
Underutilized Health Care
In addition to infrastructure challenges, many services are underutilized because of a lack of knowledge or dissuading attitudes and behaviors of a patient in regard to their medical history and future treatments. In Ethiopia, the number of days between the onset of symptoms and the first time the patient received medical care was 21 days.67
Of 47 studies conducted in sub-Saharan Africa, researchers found that between 0–63% of patients that had previously been classified as having a “good” knowledge of tuberculosis understood the causes of tuberculosis.68 Knowledge deficits among tuberculosis patients also exist regarding treatment in many areas in sub-Saharan Africa, contributing to high treatment incompletion rates. 54% of South African respondents reported that patients most often stop taking their medication because, after taking it for a few weeks, they feel better and think they are cured.69 Stigma also greatly affects initiation of treatment therapy and continued adherence. 28% of South African tuberculosis patients reported that they stopped taking their treatment medication and cited the reason as being afraid people would talk badly about them when they saw them go into the clinic. This fear of community members seeing them in the clinic also contributed to patients delaying treatment because they were afraid of what people would think.70
A perceived lack of time and finances by patients can also deter them from seeking and completing the treatment they need.71 Parents are sometimes hesitant to send their children to the clinic for suspected tuberculosis because they feel their children will be exposed to other diseases while at the healthcare facility.72
High incompletion rates for tuberculosis treatment is a major aspect of the disease’s perpetuation in sub-Saharan Africa. In 2017, only 53% of tuberculosis patients completed treatment in South Africa and only 45% in Zambia.73 However, in the United States in 2018, 87% of tuberculosis patients successfully completed treatment.74 A healthcare phenomenon called the “care cascade” explains some of these incompletions: throughout the stages of care, many patients discontinue treatment, resulting in fewer treatment completers than starters.75 The care cascade can be seen in the South African public healthcare system, where 5% of cases stopped care at test access, 13% at diagnosis, 12% at treatment initiation, and 17% at treatment completion.76
Negative Consequences
Physical Health
Individuals fighting tuberculosis experience a decrease in overall physical health, and those who survive retain lasting symptoms and weakened immunity, which causes susceptibility to other diseases and increased risk of death for the rest of their lives.
Immediate symptoms occur in individuals living with active tuberculosis such as a chronic coughing, a loss of weight and appetite, night sweats, and fever and chills, all of which were experienced by more than 95% of patients in Ethiopia.77 In Rwanda, 97% of participants reported a chronic cough, 61% reported coughing up blood, 52% described the presence of sputum, and 48% of patients reported difficulty breathing.78 These symptoms are a result of the immune system being unable to fight off the tuberculosis bacteria, resulting in multiplication of the bacteria and progression of the disease.79
Tuberculosis not only affects those that are currently fighting the disease, it also impacts the quality of life for those that have survived treatment. While treatment can be effective, a recent study found that 22% of Tanzanian participants had received treatment two or more times.80 In 2020, a study conducted in Malawi found that 61% of patients still reported respiratory symptoms at treatment completion and a separate study in Tanzania found that 45% of patients still reported respiratory symptoms after two years of treatment completion.81, 82 In Ghana, patients being treated for the second time were 69% less likely to experience treatment success.83 Among those who experience successful treatment, post-tuberculosis lung damage is prevalent which includes accelerated lung function decline, reduced quality of life, and increased susceptibility towards other diseases.84 Others reported abnormal airway obstruction and difficulty working in the year after treatment completion.85 Additionally, the long term effects of untreated tuberculosis include spinal pain, joint damage, meningitis, liver and kidney problems, and heart disorders from the spreading of bacteria in the tissues surrounding your heart.86
Increased mortality is found in those cured of tuberculosis.87 Globally, those who have been treated for tuberculosis have an increased mortality rate of 2.91 times compared to those who have never had tuberculosis.88 In Zimbabwe, those who completed treatment and survived tuberculosis were still 14.6 times more likely to die in the first year after treatment than individuals not infected with tuberculosis.89
Social Rejection
One consequence of tuberculosis particularly prevalent in sub-Saharan Africa is social rejection. 82% of tuberculosis patients in Zambia reported that they have personally been stigmatized because they had tuberculosis. These individuals were excluded from activities at school or work and slept and ate alone.90 A meta-analysis of the tuberculosis stigma in sub-Saharan Africa synthesized 15 studies and listed perceived contagiousness as a leading cause of stigmatization, in part because people associate the disease with poverty, malnutrition, and low social class.91 In Ghana, stigmatization has also led to tuberculosis patients being banned from selling goods in public markets and attending community events.92
Experiencing stigma negatively impacted social relationships in Nigeria, where 72% of respondents believed that having tuberculosis had negatively impacted their social relationships. The majority of respondents reported reduced attendance to parties and recreational events.93 Apart from merely affecting social relationships, many family members and friends of patients adopt the same stigmatizing beliefs as others and only 39.5% of respondents reported having support from a family member or friend throughout their treatment process.94 Despite completing treatment and producing multiple negative sputum samples, patients in Rwanda expressed that they would rather stay home than go out into the village because people thought they may have multi-drug resistant tuberculosis, which is very difficult to treat and could be transmitted to them.95 Anecdotes from these Rwandan patients show that some who have not been contagious for many years, but still cough up blood due to scarred lungs, have been banned from villages and left by spouses and family members because they are afraid of being contaminated.96
Community members in Zambia often associate tuberculosis with HIV and some think they are the same disease or that they are always experienced together. The stigmas regarding HIV, such as immoral behavior and a careless attitude, cause some who test positive for tuberculosis to fail to report their status.97 In one study reporting on the perceived HIV-tuberculosis association, some family members were sent to the village to live with other family members to prevent neighbors and community members from finding out their tuberculosis status.98
The stigma experienced by those infected is reported to have caused tuberculosis patients to hide their infection status, delay treatments, or discontinue treatments, For example, in Ethiopia, the total treatment delay was associated with the perceived severity of stigma, contributing to a median of 45 days delay.99 Reducing stigma around tuberculosis would increase treatment adherence, decreasing the chance for drug-resistant tuberculosis and decreasing the total number of new infections.100
Economic Burden
Many countries in sub-Saharan Africa have a free tuberculosis care policy to assist with the economic burden placed on households. While the cost of service varies in each country, the policies typically cover only the cost of the treatment medication. Despite these efforts, patients report spending astronomical percentages of their yearly household income on all other costs relating to a tuberculosis case. These costs can include clinic visits, transportation, and special foods. Patients also incur significant costs in the form of lost labor time due to the illness.
In Zambia, 27% of the total money spent on treatment was used for transport and 44% on special foods. These foods included meat, eggs, and vegetables prescribed by their doctor.101 In Kenya, the cost of travel, food, and additional tests or drugs was 55.8 USD and in Burkina Faso, 69% of the total cost was incurred from transport and special foods.102, 103 Pre-diagnosis, Zimbabwean patients reported a median cost of 25 USD for medical costs followed by a median cost of 18 USD for food. Post-diagnosis, patients reported spending 360 USD for nutritional supplements followed by 91 USD for medical costs. Overall, the total median cost per tuberculosis episode was 1,185 USD.104
Many countries in sub-Saharan Africa include a large percentage of individuals that live on less than two dollars a day. For example, in The Democratic Republic of the Congo, where 73% of the country’s population living on less than $1.90 per day, these costs can be a huge burden. In fact, 56.5% of households in a study in The Democratic Republic of the Congo incurred costs greater than 20% of their annual household expenditure.105, 106 In Benin, the median direct economic burden was 17.8% of the annual household income.107 A separate review found that the direct cost burden of tuberculosis was between 8–20% of the annual income in Zambia, Tanzania, and Malawi.108 In Nigeria, where tuberculosis treatment is also supposed to be free, the median cost was equivalent to between 9–38% of the patients’ average annual incomes.109
Apart from direct costs, illness, such as tuberculosis, can reduce one's capacity to earn income. During treatment, Zimbabwean patients lost productive time equated to a median value of 238 USD and 294.2 USD in Kenya, equivalent to 38% of the median annual income in the area.110, 111 In Benin, tuberculosis patients miss a median of 4 months of work, often resorting to coping strategies such as depleting their savings, selling assets such as land or animals, or budget cuts in areas such as housing and education for members of the household.112 These coping strategies often delay treatment such as in Chad, where selling one's belongings in order to pay for the treatment was associated with a delay of treatment, contributing to a median delay of 15 days.113 In The Democratic Republic of the Congo, 23% of tuberculosis patients lost their jobs during treatment, with 50% of all respondents being the sole provider for the household.114 It is not just patients that are affected by this disease, the amount of time lost as a caregiver was almost equal to the time lost as a patient.115 Between 3 and 87 days of labor were lost by caregivers of tuberculosis patients in Benin.116 These costs are higher for a disease like tuberculosis because of the long duration of time in the entire process of becoming ill, being diagnosed, seeking and affording treatment, and recovering. This is exacerbated when dealing with multi-drug resistant tuberculosis, which often has a longer treatment period.
Globally, the cost of tuberculosis is also very high. In 2018, 1.4 million tuberculosis deaths occured in 120 countries, resulting in $580 billion in full-income losses, $200.8 billion of which were associated with sub-Saharan Africa, the highest concentration.117 From 2020–2050, 31.8 million tuberculosis deaths are estimated to occur, resulting in an economic loss of 17.5 trillion dollars.118
Best Practice
High-Rifampicin Dose Treatment
Different areas such as increased screening and case detection, improved knowledge deficits, and social distancing may be used to pursue the mitigation of tuberculosis and its effects. Ultimately, in order to truly address the issues of tuberculosis which is endemic in many countries in sub-Saharan Africa, additional practices must be adopted to prevent further spread of the disease by those who have active tuberculosis and are infectious.119 Allocating resources and time towards preventative treatment rather than symptom treatment of tuberculosis will always be more economically sound and place fewer burdens on survivors trying to recover from tuberculosis.120 This can be achieved by ensuring that those who are infectious or may have the potential to become infectious are treated and successfully complete their treatment for the full 6–9 months. The successful treatment of each of these individuals will decrease the number of cases that progress to multi-drug resistant tuberculosis as well as decrease the total number of individuals with active tuberculosis, thus decreasing the likelihood of transmitting the disease.
Current tuberculosis treatment is lengthy, expensive, often not effective, and not well tolerated by a substantial proportion of patients.121 The long duration of tuberculosis treatment is a major barrier to adherence, which has a significant negative impact on the prevalence of tuberculosis.The symptoms of treatment such as nausea, vomiting, tingling in hands and feet, persistent fatigue, changed or blurry vision, and liver failure are often uncomfortable enough for patients to discontinue treatment.122, 123 However, recent studies have proven that increasing the dosage of certain medications can be effective in decreasing treatment time and has proven to be safe for patients. The current standard dose of one such treatment medication, rifampicin, is 10 milligrams (mg) per kilogram (kg) of body weight once per day but should not exceed 600 mg per day.124 In recent studies, administering a higher-dose of rifampicin was associated with decreased Mycobacterium tuberculosis colony counts, resulting in reduced treatment periods.125, 126, 127 Regimens of 10 and 20 mg/kg have been shown to eradicate colony counts after 14 and 11 weeks respectively where the same results were found after 8 weeks for 30 and 40 mg/kg and 6 weeks where the treatment was 50 mg/kg.128 Additionally, patients with treatment regimens with 10 mg/kg were shown to have a 86% relapse rate where regimens containing 30, 40, and 50 mg/kg had a zero percent relapse rate.129 Following this new found information, a person weighing 70 kg (154 pounds) would take a standard dose of 600 mg daily but, following new research, this same person could take 2,450 mg daily if they took 35 mg/kg. In a study conducted in Tanzania and South Africa, participants were given doses of 10, 20, and 35 mg/kg of rifampicin with no increased damage to organs or other adverse effects on the body for those who were given the highest dose, indicating that doses even greater than 35 mg/kg could be more effective.130, 131This research is newly emerging, all studies presented having been conducted in the last five years. Additional research must be conducted and the practice must become the new tuberculosis treatment standard for governing health organizations before global adoption is achieved. Early adoption of this practice will likely not reach areas in sub-Saharan Africa first due to the lack of infrastructure and resources.
Preferred Citation: Brooke Heaton. “Prevalence of Tuberculosis in Sub-Saharan Africa.” Ballard Brief. March 2022. www.ballardbrief.org.
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